A swab from an infected lesion is streaked onto a blood agar plate,a plate with blood agar that also contains colistin and nalidixic acid (a CNA plate),and a MacConkey agar plate.Growth occurs on both the blood agar and CNA plates.The organism growing must be

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Quizplus · Accepted Answer

The organism grows on both blood agar and CNA plates but not on MacConkey agar. CNA plates inhibit the growth of Gram-negative organisms, allowing for the selective isolation of Gram-positive bacteria. The lack of growth on MacConkey agar, which selects for Gram-negative, enteric bacteria, further supports that the organism is Gram-positive.

A Swab from an Infected Lesion Is Streaked onto a Blood